2023

Mesoscale Discussion #0005


Mesoscale Discussion 0005

NWS Storm Prediction Center Norman OK

0202 PM CST Mon Jan 02 2023


Areas affected...Parts of east-central OK...northeast/north-central TX...far southeast KS...northwest AR...and southwest MO


Concerning...Severe potential...Tornado Watch likely 


Valid 022002Z - 022200Z


Probability of Watch Issuance...80 percent


SUMMARY...The risk of severe storms capable of all hazards including tornadoes is increasing, and a tornado watch is likely this afternoon for much of the area.


DISCUSSION...Latest mosaic radar data shows a gradual increase in showers and isolated thunderstorms from east-central OK southward into parts of northeast TX this afternoon. This activity is developing along the western edge of the warm sector, where middle/upper 60s boundary-layer dewpoints are in place. Water vapor loops show strengthening midlevel ascent overspreading this portion of the warm sector, and cloud breaks are favoring modest boundary-layer heating/destabilization. The 18Z observed FWD/OUN soundings showed weakening convective inhibition at the base of a pronounced EML, which coupled with the increasing large-scale ascent and boundary-layer heating, should support additional thunderstorm development during the next few hours. 


Steep midlevel lapse rates atop the destabilizing boundary-layer will contribute to 1500-2000 J/kg MLCAPE over the warm sector. This moderate instability, combined with 45-55 kt of effective shear and clockwise-turning low-level hodographs (200-300 m2/s2 effective SRH) should initially support discrete or semi-discrete supercells capable of all hazards including tornadoes. These storms will generally track northeastward across the expansive warm sector, with some tendency for local upscale growth with time. A tornado watch issuance is likely for portions of the area this afternoon.


   ..Weinman/Hart.. 01/02/2023

Mesoscale Discussion #0006


Mesoscale Discussion 0006

NWS Storm Prediction Center Norman OK

0239 PM CST Mon Jan 02 2023


Areas affected...Parts of northeast TX...northwest LA...and far southwest AR


Concerning...Tornado Watch 1...


Valid 022039Z - 022215Z


The severe weather threat for Tornado Watch 1 continues.


SUMMARY...An increasingly favorable corridor for tornadoes is developing across portions of Tornado Watch 01 over parts of the Arklatex this afternoon.


DISCUSSION...Latest radar data from KPOE/KSHV shows a large cluster of showers and thunderstorms with organized embedded updrafts/mesocyclones tracking northward from southeast TX/west-central LA this afternoon. Ahead of this activity, a moist/unstable airmass characterized by upper 60s/lower 70s boundary-layer dewpoints beneath steep midlevel lapse rates (sampled by 18Z SHV sounding) are in place. Minimal convective inhibition coupled with the favorable surface-based instability across this portion of the warm sector should support the northward spread of these showers and thunderstorms during the next couple hours. And, favorable/increasing low-level hodograph curvature (150-200 m2/s2 0-1 km SRH) per SHV VWP data should support a few discrete or semi-discrete supercells capable of producing tornadoes (some possibly strong but mostly brief) and damaging gusts.


..Weinman.. 01/02/2023

Mesoscale Discussion #0049


Mesoscale Discussion 0049

NWS Storm Prediction Center Norman OK

0901 AM CST Thu Jan 12 2023


Areas affected...central into eastern MS...west-central AL...southwest AL


Concerning...Tornado Watch 17...


Valid 121501Z - 121700Z


The severe weather threat for Tornado Watch 17 continues.


SUMMARY...The risk for a couple of tornadoes will continue this morning, including the possibility for a strong tornado.  An additional tornado watch will likely need to be considered for far southeast MS into southwest and south-central AL later this morning.


DISCUSSION...Radar mosaic and single-site 88D data show a broken band of embedded cluster and quasi-discrete supercells from 40 mi WSW of Tuscaloosa extending southwestward to 30 mi W of Hattiesburg. Analysis of upper-air RAOB data this morning shows relatively cool mid-level profiles with -15.7 deg C at Birmingham and -14.1 deg C at Jackson.  Although surface dewpoints are only in the lower 60s over central AL and low-mid 60s in southern MS, the quality of the moisture through a 100-mb deep layer above the surface is notable when combined with the cool mid-level temperature profile.  RAP forecast soundings this morning into the midday hours show buoyancy around 1000 J/kg MLCAPE with large low-level hodographs.  As a result, the mesoscale environment appears favorable for a tornado risk from eastern and southeastern MS northeastward into west-central AL over the next few couple of hours.  A strong tornado is possible.  The activity over southeast LA and southern MS will eventually shift eastward into far southeast MS and southwest AL towards the midday.


..Smith.. 01/12/2023

Mesoscale Discussion #0053


Mesoscale Discussion 0053

NWS Storm Prediction Center Norman OK

1136 AM CST Thu Jan 12 2023


Areas affected...central AL


Concerning...Tornado Watch 17...


Valid 121736Z - 121900Z


The severe weather threat for Tornado Watch 17 continues.


SUMMARY...The supercell tornado risk will continue to focus over central AL through 19 UTC (1pm CST).  A strong tornado is possible.


DISCUSSION...KBMX radar imagery shows a pair of potentially tornadic supercells over central AL with a history of tornadoes in Hale County.  Surface observation trends over southern AL indicate a tendency for surface winds to veer to south-southwesterly with some mixing (lowering) of surface dewpoints at several observation sites. Farther north in the vicinity of Selma and east to Montgomery, these limiting factors for low-level mesocyclones have not been observed, hence a favorable environment for tornadoes remains across central AL.  The KBMX VAD has shown a marked intensification of low-level flow over the past 1-2 hours which is enlarging the hodograph.  With the favorable embedded to quasi-discrete supercell storm mode being maintained at least for the next 1-2 hours, expecting the tornado risk to perhaps remain relatively high before eventual supercell to squall line transition and destructive interference gradually lessen the overall tornado risk.


..Smith.. 01/12/2023

Mesoscale Discussion #55


Mesoscale Discussion 0055

NWS Storm Prediction Center Norman OK

0100 PM CST Thu Jan 12 2023


Areas affected...central AL


Concerning...Tornado Watch 18...


Valid 121900Z - 122000Z


The severe weather threat for Tornado Watch 18 continues.


SUMMARY...A strong to intense tornado (~EF3) is likely ongoing across central AL and after tornado demise, a wind-damage risk will likely continue into east-central AL.


DISCUSSION...KBMX radar imagery shows an intense low-level mesocyclone moving through an adequately moist/moderately buoyant airmass across central AL.  SPC data analytics indicates a strong/intense tornado is likely ongoing across Autauga County, AL. The area VAD/s show large hodographs with 300 m2/s2 0-0.5 km effective SRH.  The strong shear/buoyancy will likely aid in sustaining the supercell after eventual tornado demise once the squall line overtakes the supercell.  Nonetheless, a significant wind-damage threat and some tornado risk will likely continue into eastern AL through the mid afternoon.


..Smith.. 01/12/2023

Mesoscale Discussion #0093


Mesoscale Discussion 0093

NWS Storm Prediction Center Norman OK

1016 AM CST Tue Jan 24 2023


Areas affected...Middle/Upper TX Coast...Far Southwest LA


Concerning...Severe potential...Tornado Watch likely 


Valid 241616Z - 241815Z


Probability of Watch Issuance...95 percent


SUMMARY...Environmental conditions along the middle/upper TX coast into southwest LA will support supercells capable of all severe hazards, including tornadoes, this afternoon. A Tornado Watch will be needed along the middle /upper TX coast to southwest LA within the next hour or so.


DISCUSSION...Recent surface analysis places a low about 30 miles northwest of NIR in northern Bea County TX. A warm front extends east-northeastward from this low through Galveston Bay and then off the far southeast TX coast. The air mass south of this warm front is characterized by temperatures in the low 70s/upper 60s and dewpoints in the mid/upper 60s. Expectation is for this front to gradually lift northward as the surface low transitions east-northeastward. As it does, modest surface-based buoyancy is anticipated across the middle and upper TX coast. 


Robust low-level wind fields are also in place, with mesoanalysis estimating 50-60 kt at 850 mb from CRP vicinity northward into southeast TX. Southeasterly surface winds exist throughout the warm sector, resulting in strong low-level vertical shear. Recent VAD profiles from CRP and HGX sampled 300 m2/s2 and 800 m2/s2 of 0-1 km storm-relative helicity. 


Increasing thunderstorm coverage is anticipated throughout the afternoon, and these environmental conditions are expected to support strong to severe thunderstorms. More linear development is anticipated along the front south of the low, but some potential for discrete warm-sector development exists as well. Any discrete storms would likely become supercellular with the potential for all severe hazards, including tornadoes. Given the strong low-level shear, a strong tornado is possible. Large hail and damaging wind gusts are also possible. As a result, a Tornado Watch will be needed along the middle/upper TX coast in far southwest LA.


..Mosier/Hart.. 01/24/2023

Mesoscale Discussion #0189


Mesoscale Discussion 0189

NWS Storm Prediction Center Norman OK

0236 PM CST Sun Feb 26 2023


Areas affected...Southwest KS...Eastern TX/OK Panhandles...Western OK


Concerning...Severe potential...Tornado Watch likely 


Valid 262036Z - 262230Z


CORRECTED TO INCREASE WATCH PROBABILITY


Probability of Watch Issuance...95 percent


SUMMARY...Fast-moving supercells capable of all severe hazards, including significant wind gusts over 80 mph, very large hail greater than 2 inches in diameter, and tornadoes, are expected to develop across the region this afternoon and evening. A Tornado Watch will be needed within the next hour or two.


DISCUSSION...Significant air mass modification continues across the southern Plains ahead of an intense upper low moving out of the Southwest. Much of the eastern TX and OK Panhandles and western OK have experienced dewpoint increases of 4 to 8 deg F over the past 3 hours. This modification is expected to continue as large-scale forcing for ascent attendant to the approaching low increases, likely resulting in thunderstorm initiation during the next hour or two from southwest KS across the eastern OK and TX Panhandles and into northwest TX. 


Wind fields, which are already quite strong, are expected to further strengthen as the system approaches. Current mesoanalysis estimates the 0-6 km shear is already 70 kt, with forecast soundings suggesting an increase to 85-90 kt is anticipated by 00Z. Forecast hodographs also show robust low veering with height, supported by 50-60 kt flow around 1 km. Forecast soundings show surface to 500 m storm-relative helicity is over 300 m2/s2 across the eastern TX and OK Panhandles at 00Z.


These environmental conditions are very supportive of supercells capable of all severe hazards, including significant wind gusts over 80 mph, very large hail greater than 2 inches in diameter, and tornadoes. Upscale growth into a linear convective line is anticipated, with strong wind gusts and embedded tornadoes possible once this transition occurs. A Tornado Watch will be needed in the next hour or two to cover this potential.


..Mosier/Grams.. 02/26/2023

Mesoscale Discussion #0196


Mesoscale Discussion 0196

NWS Storm Prediction Center Norman OK

0753 PM CST Sun Feb 26 2023


Areas affected...portions of western into central OK


Concerning...Tornado Watch 43...44...


Valid 270153Z - 270330Z


The severe weather threat for Tornado Watch 43, 44 continues.


SUMMARY...A swath of intense damaging gusts and possibly a tornado will shift east/northeast from western into central OK over the next 1-2 hours.


DISCUSSION...An intense bowing segment with an eastward-advancing line of convection was located near Kiowa and Washita Counties in western OK. Measured gusts from the Oklahoma Mesonet between 62 and 78 mph have been noted with this area of convection over the past 30-60 minutes. This area of storms will continue tracking east/northeast at around 60-70 mph, bringing a swath of intense damaging gusts toward the OKC Metro vicinity by 9pm CST. Wind gusts to 80-90 mph appear possible with this convection. Additionally, given intense low-level shear, mesovortex tornadoes also will be possible.


..Leitman.. 02/27/2023

Mesoscale Discussion #0207


Mesoscale Discussion 0207

NWS Storm Prediction Center Norman OK

0113 PM CST Mon Feb 27 2023


Areas affected...Parts of Southwestern Ohio


Concerning...Tornado Watch 47...


Valid 271913Z - 272015Z


The severe weather threat for Tornado Watch 47 continues.


SUMMARY...A local corridor of greater tornado potential is evident in southwestern Ohio.


DISCUSSION...Two storms along the Ohio/Indiana border, west of Cincinnati and Dayton, are moving northeast. These storms have exhibited strong mid-level rotation on KIND/KILN radar velocity data. The downstream environment has warmed into the mid 60s F (and 70 F at KHAO). Local WSR-88D and TDWR VAD profiles continue to show enlarged low-level hodographs despite some veering of winds as boundary-layer mixing has increased. This region of southwest Ohio will be the focus for tornado potential over the next hour or so.


..Wendt.. 02/27/2023

Mesoscale Discussion #0219


Mesoscale Discussion 0219

NWS Storm Prediction Center Norman OK

0844 PM CST Wed Mar 01 2023


Areas affected...southeastern Arkansas...northwestern Mississippi


Concerning...Tornado Watch 50...


Valid 020244Z - 020345Z


The severe weather threat for Tornado Watch 50 continues.


SUMMARY...Mature/intense supercell is moving across southeastern Arkansas, accompanied by very large hail and the potential to produce a tornado.


DISCUSSION...A long-lived, strongly rotating supercell is currently moving east-southeastward across Lincoln County Arkansas at this time.  The storm continues to exhibit a large/strongly rotating mesocyclone, per KLZK WSR-88D, and appears to be producing very large hail.  


The storm is moving along a low-level conglomerate/convective boundary lying west-to-east across southeastern Arkansas and northern Mississippi.  Given the maximized baroclinic low-level vorticity along the boundary, there is some potential that this storm could produce a strong tornado over the next 30 to 60 minutes.


..Goss.. 03/02/2023

Mesoscale Discussion #0244


Mesoscale Discussion 0244

NWS Storm Prediction Center Norman OK

1015 AM CST Fri Mar 03 2023


Areas affected...much of Kentucky...far southern Indiana...Middle Tennessee...northern Alabama


Concerning...Tornado Watch 60...


Valid 031615Z - 031915Z


The severe weather threat for Tornado Watch 60 continues.


SUMMARY...The threat for tornadoes will increase through the afternoon, from near the Ohio River southward into northern Alabama and eventually Georgia. Additional watches are likely later today east of ongoing tornado watch #60.


DISCUSSION...A surface low near the IL/KY border will continue to deepen today as it travels up the OH River Valley and near a warm front. Areas of thunderstorms are ongoing near the low, with an arcing line of cells extending south into northern AL. Breaks in the clouds as well as strong southerly advection will continue to destabilize the warm sector, with sufficient instability forecast to support supercells with tornadoes by afternoon. Limited instability near the warm front will be mitigated by very strong lift combined with cooling aloft, and these height falls will extend southward into Middle TN. Midlevel lapse rates will be steeper beneath the midlevel wave, with the surface low track and warm front zone being a favored area for tornadoes, some strong. Initial convection near the low has periodically shown signs of rotation.


Ongoing storms from middle TN into northwest AL will continue to strengthen as well, aided by higher boundary-layer theta-e despite being south of the midlevel jet core. Very strong shear is in place across the entire region, favoring fast-moving supercells and tornado threat.


..Jewell/Grams.. 03/03/2023

Mesoscale Discussion #0324


Mesoscale Discussion 0324

NWS Storm Prediction Center Norman OK

0456 PM CDT Fri Mar 24 2023


Areas affected...Northeastern LA...southeastern AR...western MS


Concerning...Severe potential...Tornado Watch likely 


Valid 242156Z - 250000Z


Probability of Watch Issuance...95 percent


SUMMARY...The supercell tornado risk will gradually increase over the next couple hours across portions of the Lower MS Valley. Several tornadoes (some strong to intense) are possible. A tornado watch will be needed in the next 30-60 min.


DISCUSSION...Latest surface observations show rich boundary-layer moisture (middle/upper 60s dewpoints) spreading northward across portions of the Lower MS Valley -- aided by ongoing cyclogenesis near the ArkLaTex vicinity. Earlier diurnal heating and a strengthening low-level jet over the warm sector have aided in the development of north/south-oriented confluence bands extending from LA northward into southeastern AR and western MS. Isolated convection is evolving along these bands in the warm sector -- ahead of a primary pre-frontal trough farther west.


During the next couple hours, these storms should continue spreading northward and maturing as large-scale ascent and surface pressure falls continue amid increasing boundary-layer moisture. The downstream environment will feature enlarging/clockwise-turning low-level hodographs favorable for increasingly organized cyclonic supercells. And, given the subtle low-level forcing mechanism, a discrete or semi-discrete mode is possible for at least a few hours. Therefore, the supercell tornado risk (some strong to intense) will gradually increase as storms mature during the next few hours, with large hail and locally damaging winds also possible. A tornado watch will likely be issued in the next 30-60 min.


..Weinman/Thompson.. 03/24/2023

Mesoscale Discussion #0328


Mesoscale Discussion 0328

NWS Storm Prediction Center Norman OK

0639 PM CDT Fri Mar 24 2023


Areas affected...Parts of northeast LA...southeast AR...and west-central MS


Concerning...Tornado Watch 76...


Valid 242339Z - 250115Z


The severe weather threat for Tornado Watch 76 continues.


SUMMARY...Supercells should intensify during the next hour or so, with a corresponding increase in tornado potential.


DISCUSSION...A favorable corridor for supercell intensification is evolving over portions of northeastern LA, southeast AR, and west-central MS this afternoon/early evening. Here, boundary-layer moisture is increasing (middle/upper 60s dewpoints) amid substantial surface pressure falls beneath a strengthening low-level jet (around 50 kt at 850 mb per DGX VWP). The corresponding DGX VWP hodograph has increased in both size and clockwise curvature during the last few hours, with nearly 200 m2/s2 0-1 km SRH sampled at DGX. As the low-level jet strengthens further, hodographs should only get larger along/south of an east/west-oriented marine front shifting northward. Current thinking is that a few supercell clusters near the MS river will intensify as they track northeastward into this increasingly favorable environment during the next hour or so, with a corresponding increase in tornado potential (some strong to intense).


..Weinman.. 03/24/2023

Mesoscale Discussion #329


Mesoscale Discussion 0329

NWS Storm Prediction Center Norman OK

0824 PM CDT Fri Mar 24 2023


Areas affected...North-central MS


Concerning...Tornado Watch 76...


Valid 250124Z - 250215Z


CORRECTED FOR ERROR IN SPATIAL DELINEATION


The severe weather threat for Tornado Watch 76 continues.


SUMMARY...An intense tornado (EF3+) is likely ongoing with a supercell tracking northeastward across western Sharkley County MS, and this storm should persist for the next 30-60 min.


DISCUSSION...Latest radar data shows an organized cyclonic supercell tracking northeastward across western Sharkley County MS, with a VROT above 70 kt and well-defined TDS up to 13k ft -- indicative of an intense tornado (EF3+) given the parameter space (STP of 4). The downstream environment features a large, clockwise-curved hodograph per DGX VWP (around 430 m2/s2 0-1 km SRH) amid rich boundary-layer moisture. This will support the maintenance of this intense supercell toward the northeast for the next 30-60 min.


   ..Weinman.. 03/25/2023

Mesoscale Discussion #0332


Mesoscale Discussion 0332

NWS Storm Prediction Center Norman OK

0927 PM CDT Fri Mar 24 2023


Areas affected...Parts of north-central into northeastern MS


Concerning...Tornado Watch 76...


Valid 250227Z - 250330Z


The severe weather threat for Tornado Watch 76 continues.


SUMMARY...Strong to intense (EF2-EF3) tornado threat should continue northeastward across parts of north-central and northeastern MS in a favorable environment.


DISCUSSION...An intense northeastward-moving tornadic supercell is ongoing across Carroll County MS, with recent VROTs around 70 kt and deep/well-defined TDS. This storm still has plenty of residence time in the open warm sector as boundary-layer moisture surges north into north-central into northeastern MS -- characterized by middle/upper 60s surface dewpoints. This favorable boundary-layer moisture, coupled with large looping hodographs (around 400 m2/s2 0-1 km SRH) sampled by the GWX VWP should support a continued threat of a strong to intense tornado during the next 30-60 min.


..Weinman.. 03/25/2023

Mesoscale Discussion #0333


Mesoscale Discussion 0333

NWS Storm Prediction Center Norman OK

0957 PM CDT Fri Mar 24 2023


Areas affected...Northeastern MS into northwestern AL


Concerning...Tornado Watch 76...77...


Valid 250257Z - 250400Z


The severe weather threat for Tornado Watch 76, 77 continues.


SUMMARY...Severe threat, including the potential for strong tornadoes and damaging winds, continues across parts of northeastern MS into northwestern AL.


DISCUSSION...Latest radar data from GWX depicts a well-organized supercell cluster tracking east-northeastward across northeastern MS this evening. Ahead of this storm, lower 60s dewpoints are spreading northward in response to continued cyclogenesis to the north -- supporting surface-based inflow. With a strengthening low-level jet over the area (70+ kt 850-mb winds) sampled by the GWX VWP, hodographs are becoming increasingly favorable for intense supercells (even if embedded in line segments). Given the ample streamwsie vorticity and surface-based inflow for this storm, strong tornadoes and damaging winds remain possible from northeastern MS into northwestern AL.


..Weinman.. 03/25/2023

Mesoscale Discussion #0365


Mesoscale Discussion 0365

NWS Storm Prediction Center Norman OK

0747 PM CDT Sun Mar 26 2023


Areas affected...Portions of south-central Alabama


Concerning...Tornado Watch 89...


Valid 270047Z - 270215Z


The severe weather threat for Tornado Watch 89 continues.


SUMMARY...A locally favorable corridor for supercell tornadoes may be developing over portions of south-central AL (near and just south of Montgomery) during the next couple hours.


DISCUSSION...Latest surface observations and radar/satellite imagery indicate a remnant outflow boundary extending east/southeastward from near/south of Montgomery AL into southeast AL. Through this corridor, dewpoints remain in the middle/upper 60s and surface winds are relatively backed. While somewhat removed from this area, the LIX 00Z observed sounding shows deep boundary-layer moisture beneath steep midlevel lapse rates (supporting a deep effective inflow layer), and this should be somewhat representative of the environment spreading into south-central AL. In addition, regional VWPs show a modest increase in low-level flow, and further strengthening should yield larger/clockwise-turning low-level hodographs with time. If the supercell cluster in Wilcox County/southern Dallas County continues eastward along the outflow boundary, the aforementioned environment could favor increasing tornado potential with this storm (or additional storms that can develop into this environment) during the next couple hours.


..Weinman.. 03/27/2023

Mesoscale Discussion #0370


Mesoscale Discussion 0370

NWS Storm Prediction Center Norman OK

0304 AM CDT Mon Mar 27 2023


Areas affected...east-central Alabama


Concerning...Severe potential...Watch unlikely 


Valid 270804Z - 271000Z


Probability of Watch Issuance...20 percent


SUMMARY...Risk for a tornado is locally enhanced over parts of east-central Alabama and adjacent far west-central Georgia.  WW issuance is not anticipated due to local nature of the risk.


DISCUSSION...Latest surface data indicates an outflow-enhanced, west-to-east segment of the surface boundary lying across eastern Georgia, where Auburn, AL and Columbus, GA obs sites show easterly flow, with sites just to the south depicting southerlies.  This boundary also marks the northern fringe of near 70 dewpoints, and associated zone of maximized CAPE.


An earlier storm that moved through Macon County AL acquired rotation in proximity to this boundary (around 0630Z), and now a second storm has organized, as it shifted across northern Montgomery County and now into Macon/far southeastern Elmore Counties.


This storm has acquired much stronger rotation than the earlier storm, with 60 kt rotational velocity and a TDS (local minimum in WSR-88D correlation coefficient) indicative of a potentially strong tornado occurring at this time.


With that said, the area of maximized potential appears to be very local, with uncertainty as to whether any additional storm will occur within this small zone.  As such, WW issuance is not anticipated at this time, but we will continue to monitor for any signs of increasing potential over a broader geographic area.


..Goss/Grams.. 03/27/2023

Mesoscale Discussion #390


Mesoscale Discussion 0390

NWS Storm Prediction Center Norman OK

1037 AM CDT Fri Mar 31 2023


Areas affected...portions of southeastern Iowa...northwestern Illinois...and far northeastern Missouri


Concerning...Outlook upgrade 


Valid 311537Z - 311630Z


SUMMARY...Portions of the Moderate Risk over southeastern IA, northwestern IL, and far northeastern MO will be upgraded to a categorical High Risk in the 1630 UTC Convective outlook.


DISCUSSION...An upgrade to a tornado-driven High Risk (30% probability) is expected for the 1630 UTC outlook. Environmental conditions are quickly becoming favorable to support the potential for numerous strong to potentially violent and long-track tornadoes across portions of southeastern IA, northwestern IL, and far northeastern MO. Please see the forthcoming Day 1 outlook update for more information.


   ..Lyons/Smith.. 03/31/2023

Mesoscale Discussion #0391


Mesoscale Discussion 0391

NWS Storm Prediction Center Norman OK

1044 AM CDT Fri Mar 31 2023


Areas affected...ArkLaTex into parts of the Mid South


Concerning...Severe potential...Tornado Watch likely 


Valid 311544Z - 311745Z


Probability of Watch Issuance...95 percent


SUMMARY...The threat for tornadic supercells will increase this afternoon. PDS Tornado Watch issuance is eventually expected for parts of the region.


DISCUSSION...Weak elevated convection has been ongoing across parts of AR this morning, within a plume of rich low-level moisture and along the periphery of a lead shortwave moving across eastern portions of the central Plains. Additional convective development has been noted recently into southeast OK and northeast TX. Widespread cloudiness will tend to limit diurnal heating to some extent, but gradual warming amid increasingly rich low-level moisture will support MLCAPE increasing into the 1000-2000 J/kg range and weakening MLCINH with time. 


Area VWPs already depict very favorable wind profiles, with strong low-level (0-1 km SRH of 200-400 m2/s2) and deep-layer shear (effective shear of 60+ kt) expected to persist through the day. Tornadic supercells are expected to eventually evolve across the region this afternoon, with a few longer-lived supercells capable of producing strong/intense tornadoes possible, especially across AR toward the MS Valley. Onset timing of the greater threat remains somewhat uncertain, but one or more Tornado Watches will be required by early afternoon, with PDS Tornado Watch issuance expected across parts of AR toward the MS Valley.


..Dean/Hart.. 03/31/2023

Mesoscale Discussion #392


Mesoscale Discussion 0392

NWS Storm Prediction Center Norman OK

1047 AM CDT Fri Mar 31 2023


Areas affected...portions of eastern Arkansas...southwestern Tennessee...and northern Mississippi


Concerning...Outlook upgrade 


Valid 311547Z - 311645Z


SUMMARY...Portions of the Moderate Risk area over eastern AR, southwestern TN, and northern MS will be upgraded to a categorical High Risk in the 1630 UTC Convective outlook.


DISCUSSION...An upgrade to a tornado-driven High Risk (30% probability) is expected for the 1630 UTC outlook. Environmental conditions are quickly becoming favorable to support the potential for numerous strong to potentially violent and long-track tornadoes across portions of eastern AR, southwestern TN, and northern MS. Please see the forthcoming Day 1 outlook update for more information.


   ..Lyons/Smith.. 03/31/2023

Mesoscale Discussion #0393


Mesoscale Discussion 0393

NWS Storm Prediction Center Norman OK

1124 AM CDT Fri Mar 31 2023


Areas affected...portions of eastern Iowa...northern Missouri and northwestern Illinois


Concerning...Severe potential...Tornado Watch likely 


Valid 311624Z - 311800Z


Probability of Watch Issuance...95 percent


SUMMARY...Rapid supercell development is expected over the next 1 to 2 hours across portions of southwestern IA and northern MO. As storms mature the risk for strong and long-track tornadoes, large hail and damaging winds is expected to increase quickly through the early afternoon. A PDS Tornado Watch is likely need soon.


DISCUSSION...As of 1600 UTC, visible satellite imagery showed deepening cumulus and initial thunderstorms developing over portions of far northeastern KS and northern MO. Located beneath the left exit region of a powerful 100+ kt mid-level jet, large-scale dynamic lift will continue to increase over a rapidly destabilizing warm sector. SPC mesoanalysis and area RAP soundings show minimal inhibition remains across the western part of the warm sector where strong diurnal heating is ongoing. Farther northeast the airmass remains somewhat sheltered with lingering cirrus, but dewpoints in the upper 50s to low 60s F and steep mid-level lapse rates were supporting 1000-1500 J/kg of MLCAPE. Incipient thunderstorms should develop within the deepening cumulus field and spread quickly northeastward into a strongly sheared (ESRH 300-400 m2/s2) environment. The current observational tends match consistently with recent HRRR and WOFS guidance which shows numerous, potentially tornadic, supercells moving across eastern IA this afternoon. In addition, large to very large hail will be possible with storms given cold temps aloft and strong vertical shear. Given the significant threat for strong/long-track tornadoes, a PDS tornado watch will likely be needed within the next hour.


..Lyons/Hart.. 03/31/2023

Mesoscale Discussion #0399



Mesoscale Discussion 0399

NWS Storm Prediction Center Norman OK

0142 PM CDT Fri Mar 31 2023


Areas affected...Southwest into central AR


Concerning...Tornado Watch 94...


Valid 311842Z - 312015Z


The severe weather threat for Tornado Watch 94 continues.


SUMMARY...A corridor of strong tornado potential may develop through mid afternoon as supercells move east-northeastward.


DISCUSSION...At 1830 UTC, scattered supercells have developed from southwest into central AR, with increasing midlevel rotation noted with cells immediately west and southwest of Little Rock. Recent mesoanalyses and the LZK VWP continue to show 0-1 km and effective SRH in excess of 300 m2/s2, with some stronger heating noted just to the south of the southernmost cells. With MLCAPE in excess of 1500 J/kg across the region and very favorable wind profiles, tornado potential is expected to ramp up through mid afternoon. The greatest threat of a strong tornado is expected over a corridor across central AR for the next 1-2 hours.


..Dean.. 03/31/2023

Mesoscale Discussion #0401


Mesoscale Discussion 0401

NWS Storm Prediction Center Norman OK

0236 PM CDT Fri Mar 31 2023


Areas affected...Central Arkansas


Concerning...Tornado Watch 94...


Valid 311936Z - 312000Z


The severe weather threat for Tornado Watch 94 continues.


SUMMARY...A confirmed tornado is ongoing within the southwestern Little Rock metro area. Downstream environment will remain favorable for this tornado to continue.


DISCUSSION...A tornadic supercell now entering the Little Rock metro area has shown increasing organization over the last 30 minutes.  As of 223 PM CDT a confirmed tornado was moving northeastward. The KLZK VAD shows strong veering in the lowest 1 km (over 400+ SRH). VROT was observed to be 74 kts. Given the environment and radar signature, this would suggest a likely intense (EF3) tornado. Furthermore the low/mid 60s F dewpoints downstream and unimpeded inflow, the expectation is for this storm to continue to pose a threat for potentially strong tornado over the next hour at least.


..Wendt.. 03/31/2023

Mesoscale Discussion #0407


Mesoscale Discussion 0407

NWS Storm Prediction Center Norman OK

0359 PM CDT Fri Mar 31 2023


Areas affected...Southeast Iowa


Concerning...Tornado Watch 93...


Valid 312059Z - 312130Z


CORRECTED FOR AREAS AFFECTED


The severe weather threat for Tornado Watch 93 continues.


SUMMARY...Likely strong tornado (upper EF2 to EF3) ongoing northeast of Ottumwa. The downstream environment will continue to support the potential for a strong tornado.


DISCUSSION...A supercell northeast of Ottumwa has shown increasing low-level rotation with a tornado recently confirmed. Current VROT observations from KDMX are around 60 kts. Given the environment, this would suggest a strong tornado (EF2-EF3) is likely ongoing. The deepening surface low and continued backed surface winds in eastern Iowa will continue to support a strong/intense tornado threat as this storm continues to the north and east.

Mesoscale Discussion #0409


Mesoscale Discussion 0409

NWS Storm Prediction Center Norman OK

0514 PM CDT Fri Mar 31 2023


Areas affected...Northeast Arkansas into western Tennessee


Concerning...Tornado Watch 94...


Valid 312214Z - 312245Z


The severe weather threat for Tornado Watch 94 continues.


SUMMARY...A strong (EF2) tornado likely occurred in northeastern Arkansas, north-northwest of Memphis. The downstream environment will continue to support the potential for additional EF2+ tornadoes.


DISCUSSION...Rotational velocity observations of 50-65 kts from KNQA across Cross County, AR suggest a likely EF2 tornado occurred. While the velocity signature has shown some disorganization over the last several minutes, a strong mesocyclone remains and the downstream environment will continue to support the potential for additional strong (EF2+) tornadoes as the KNQA VAD shows over 500 m2/s2 SRH.


..Wendt.. 03/31/2023

Mesoscale Discussion #0412


Mesoscale Discussion 0412

NWS Storm Prediction Center Norman OK

0530 PM CDT Fri Mar 31 2023


Areas affected...Eastern Iowa...Western Illinois...Northeast Missouri...Extreme Southwest Wisconsin


Concerning...Tornado Watch 93...


Valid 312230Z - 010030Z


CORRECTED FOR WORDING DISCUSSION PARAGRAPH


The severe weather threat for Tornado Watch 93 continues.


SUMMARY...Tornadoes, very large hail and widespread wind damage will be likely across the northern and eastern part of WW 93 over the next 2 to 4 hours. The greatest severe threat will exist from eastern Iowa into western Illinois and northeastern Missouri.


DISCUSSION...The WSR-88D high-resolution radars in Iowa at Des Moines and Davenport show four severe line-segments ongoing in eastern Iowa, with several tornadic supercells ongoing. These storms are located to the east of a 986 mb surface low, along a north-to-south axis of moderate instability. A 90 to 110 knot mid-level jet is translating quickly northeastward toward the Mid Mississippi Valley at near 50 knots. The left exit region of the mid-level jet is moving across eastern Iowa and western Illinois, and is creating strong deep-layer shear and enhanced lift, favorable for intense supercells. Ahead of the mid-level jet, a 50 to 60 knot low-level jet will strengthen over the next few hours across the mid Mississippi Valley. This feature will maintain low-level shear very favorable for tornadic supercells. RAP forecast soundings increase 0-3 km storm-relative helicity into the 400 to 450 m2/s2 range across northwestern Illinois early this evening, suggesting the tornado threat will increase there. Over the next few hours, the most favorable corridor for long-track high-end tornadoes will be from eastern Iowa into northwest Illinois.


In addition to the tornado threat, several swaths of wind damage will be likely with bowing line segments. This potential could increase over the next few hours, especially if the line segments can accelerate in forward speed. Due to the steep mid-level lapse rates, strong deep-layer shear and relatively cold temperatures aloft, supercells will also likely be prolific hail producers.


..Broyles.. 03/31/2023

Mesoscale Discussion #0415


Mesoscale Discussion 0415

NWS Storm Prediction Center Norman OK

0659 PM CDT Fri Mar 31 2023


Areas affected...central Arkansas...far northwestern

Mississippi...and far southwestern Tennessee


Concerning...Tornado Watch 94...


Valid 312359Z - 010100Z


CORRECTED FOR LOCATION IN HEADLINE AND TEXT


The severe weather threat for Tornado Watch 94 continues.


SUMMARY...Tornado threat increasing over the next few hours.


DISCUSSION...Two discrete supercells across east central Arkansas near the Mississippi and Tennessee borders have shown signs of better organization over the last hour. The southern of the two cells has a history of large hail up to 1.75". These supercells are tracking northeastward rapidly around 40-50 mph into a very favorable environment near and south of the Memphis metro. The VAD profile from KNQA (Memphis, Tennessee) shows observed 0-1km SRH around 530 m2/s2. 0-3 km SRH is observed at around 700 m2/s2. In addition, surface objective analysis shows SBCAPE around 1000-1500 J/kg, with the area near and just south of the Memphis area largely undisturbed from earlier storms across the northern edge. This environment continues to support long-track supercells with potential for strong tornadoes. As these cells continue a northeastward track they are expected to maintain intensity, given their discrete nature and downstream favorable environment. The tornado potential will increase across east Central Arkansas into western Tennessee and far northwestern Mississippi over the next few hours.


..Thornton/Edwards.. 03/31/2023

Mesoscale Discussion #0418


Mesoscale Discussion 0418

NWS Storm Prediction Center Norman OK

0849 PM CDT Fri Mar 31 2023


Areas affected...west Tennessee and far northern Mississippi


Concerning...Tornado Watch 97...


Valid 010149Z - 010345Z


The severe weather threat for Tornado Watch 97 continues.


SUMMARY...Greatest tornado threat over the next couple of hours will be north of the Mississippi/Tennessee border.


DISCUSSION...A long-track supercell is north of the MS/TN border just north of Highway 72 near Slayden and Mount Pleasant in MS. This cell has a history of producing tornadoes with a recent report of a confirmed large and extremely dangerous tornado. This supercell should maintain intensity over the next couple of hours, given strong low-level shear and ample instability ahead of the track. Surface objective analysis shows SRH around 300-400 m2/s2 increasing with northward extent amid SBCAPE of around 1000 J/kg. This will continue to be a dangerous storm with the potential to produce strong tornadoes as it tracks northeast towards Highway 64 near Bolivar and Hornsby.


..Thornton/Edwards.. 04/01/2023

Mesoscale Discussion #456


Mesoscale Discussion 0456

NWS Storm Prediction Center Norman OK

0149 PM CDT Tue Apr 04 2023


Areas affected...portions of central/southern IA...northwest IL and northern MO


Concerning...Severe potential...Tornado Watch likely 


Valid 041849Z - 042045Z


Probability of Watch Issuance...95 percent


SUMMARY...Supercell thunderstorms are expected to develop by 22z/5 pm CDT and shift east across central/southern Iowa, northern Missouri and northwest Illinois through the evening. These storms will be capable of producing very large hail, tornadoes (some strong) and damaging gusts. A tornado watch will likely be issued in the next couple of hours.


DISCUSSION...Northward transport of low-level moisture continues early this afternoon. Dewpoints across southern IL/northern MO into northwest IL have increased 8 degrees F over the past 3 hours. Strong heating to the south of a warm front has resulting in temperatures into the low/mid 80s F amid low/mid 60s F surface dewpoints. Some midlevel dry air is evident in forecast and observed soundings, and may result in some mixing of boundary-layer moisture. Forecast guidance suggest an increasing low-level jet will nose into the eastern IA/northwest IL later this afternoon and support open warm sector storms near the warm front. Additional storms are expected to develop near the surface low, southward along the eastward-advancing dryline/cold front. While mixing may result in somewhat higher LCLs, very steep midlevel lapse rates and strong vertical shear will support supercells capable of very large hail (greater than 3 inch in diameter) and damaging gusts. Furthermore, forecast soundings indicated favorable low-level shear and 0-1 km SRH increasing to around 250 m2/s2, supporting tornado potential. 


Increasing cumulus is noted in latest visible satellite imagery both along the warm front and ahead of the dryline as of 1830z. A couple of elevated cells have even started to develop southward into west-central MO. While capping remains over the region, this may be an indication of some increased forcing beginning to impinge on the area. Continued low-level warm/moist advection beneath the cap, coupled with heating and gradual increasing ascent should result in greater convective initiation/coverage by around 22z. A tornado watch will be likely in the next couple of hours.


..Leitman/Hart.. 04/04/2023

Mesoscale Discussion #475


Mesoscale Discussion 0475

NWS Storm Prediction Center Norman OK

0203 AM CDT Wed Apr 05 2023


Areas affected...portions of central and northern AR


Concerning...Tornado Watch 121...


Valid 050703Z - 050830Z


The severe weather threat for Tornado Watch 121 continues.


SUMMARY...A potential tornadic supercell corridor is beginning to focus from near Russellville northeastward into southeast MO (thru 330am).  A strong tornado is possible.


DISCUSSION...Radar imagery over the past hour has shown further intensification of storms over north-central AR with the stronger storms acquiring transient supercell characteristics.  Recent subjective surface mesoanalysis shows a moisture axis (upper 60s degree F dewpoints) extending from central AR north-northeastward into northern AR and immediately east of the ongoing storms.  The presence of moderate buoyancy (1800 J/kg MLCAPE per the Batesville, AR RAP-model forecast sounding) and strongly sheared low levels, will support the potential for longer-lived supercells with episodic strengthening of the low-level mesocyclone and tornado potential. If one or more of the supercells continues to mature and strengthen, a strong tornado is possible.


   ..Smith.. 04/05/2023

Mesoscale Discussion #477


Mesoscale Discussion 0477

NWS Storm Prediction Center Norman OK

0348 AM CDT Wed Apr 05 2023


Areas affected...southeast MO...far southern IL


Concerning...Tornado Watch 121...


Valid 050848Z - 050915Z


The severe weather threat for Tornado Watch 121 continues.


SUMMARY...Based on recent radar velocity and environmental data, a strong tornado (EF2-EF3) is likely ongoing.  The risk for a longer track strong tornado will likely persist and spread northeastward perhaps into southern IL through 430am.


DISCUSSION...An intense supercell is moving northeastward across southeast MO within a plume of rich low-level moisture immediately east of the supercell (mid 60s dewpoints).  Area 88D VAD show enlarged low-level hodographs (around 400 0-1km SRH with the observed storm motion per KPAH).  The strong deep-layer shear coupled with the moderate buoyancy has promoted the development of long-lived supercells.  Expecting a continuation of the strong-tornado threat to persist downstream into southern IL over the next hour or so.


   ..Smith.. 04/05/2023

Mesoscale Discussion #481


Mesoscale Discussion 0481

NWS Storm Prediction Center Norman OK

0625 AM CDT Wed Apr 05 2023


Areas affected...far northern AR...far southern MO


Concerning...Tornado Watch 124...


Valid 051125Z - 051300Z


The severe weather threat for Tornado Watch 124 continues.


SUMMARY...Tornadic supercell potential will likely focus near the AR/MO border through 8am.  A strong tornado is possible.


DISCUSSION...A pair of discrete supercells have developed over the Ozarks ahead of a broken squall line located on a cold front.  The airmass ahead of the squall line in the warm sector is moderately unstable (2500 J/kg MLCAPE) and features a moisture-rich low-level airmass (upper 60s dewpoints over northern AR).  Rapid storm motions (50 kt to the northeast) indicate around 450 m2/s2 0-1km SRH is present over northern AR per KLZK VAD data.  As these supercells continue to mature and cycle, the tornado risk will probably increase with one or both of the supercells.  A strong tornado (EF2-EF3) is possible.


   ..Smith.. 04/05/2023

Mesoscale Discussion #565


Mesoscale Discussion 0565

NWS Storm Prediction Center Norman OK

0802 PM CDT Wed Apr 19 2023


Areas affected...portions of central Oklahoma


Concerning...Tornado Watch 147...148...


Valid 200102Z - 200230Z


The severe weather threat for Tornado Watch 147, 148 continues.


SUMMARY...A large hail threat will continue for another 2 to 3 hours with the potential for a few tornadoes.


DISCUSSION...Multiple supercells are ongoing from north-central to south-central Oklahoma with hail up to baseball size and a few tornadoes. These storms have been mostly hail producers with only weak/brief low-level circulations. However, a storm merger in McClain county combined with increasing SRH as the low-level jet strengthens led to a strong tornado with a TDS above 10kft and a Vrot of 80-85 knots with a STP of 3-4. This suggests damage potential consistent with a strong to intense tornado (potentially 150+ mph)


While the ongoing tornado appears to be occluding, additional reorganization/restrengthening could pose a significant tornado threat for another 1 to 2 hours at it moves east.


   ..Bentley.. 04/20/2023

Mesoscale Discussion #568


Mesoscale Discussion 0568

NWS Storm Prediction Center Norman OK

0931 PM CDT Wed Apr 19 2023


Areas affected...Portions of east-central Oklahoma in the vicinity of I-40.


Concerning...Tornado Watch 147...


Valid 200231Z - 200330Z


The severe weather threat for Tornado Watch 147 continues.


SUMMARY...Tornado threat continues across portions of central Oklahoma, including the Interstate 40 corridor.


DISCUSSION...A HP cluster of storms across central Oklahoma has become messy, but continues to cycle, producing several tornadoes, some which may be strong to intense. Vrot values have been as high as 90 knots in the last 30 minutes with STP of 4 to 5 indicating the potential for strong to potentially intense tornadoes. The messy nature of the supercells has led to deviant tornado motions which will likely continue until the demise of the cluster. This cluster may eventually move into Hughes county and watch 147 may eventually need to be extended.


   ..Bentley/Guyer.. 04/20/2023

Mesoscale Discussion #647


Mesoscale Discussion 0647

NWS Storm Prediction Center Norman OK

0142 PM CDT Fri Apr 28 2023


Areas affected...central TX


Concerning...Tornado Watch 177...


Valid 281842Z - 282015Z


The severe weather threat for Tornado Watch 177 continues.


SUMMARY...The potential for a strong tornado will increase during the 200-300pm period over a small part of central TX.  Giant hail (diameter 3 inches or larger) is also possible.


DISCUSSION...A discrete supercell has recently developed near a triple point in Hamilton County.  Surface observations show a plume of mid-upper 60s dewpoints immediately southeast of the supercell. RAP forecast soundings show quickly enlarging hodographs over the next hour or so with 250-300 m2/s2 effective SRH.  A strong tornado is possible.


   ..Smith.. 04/28/2023

Mesoscale Discussion #651


Mesoscale Discussion 0651

NWS Storm Prediction Center Norman OK

0323 PM CDT Fri Apr 28 2023


Areas affected...central TX


Concerning...Tornado Watch 177...


Valid 282023Z - 282130Z


The severe weather threat for Tornado Watch 177 continues.


SUMMARY...An intense supercell ongoing in Coryell, County TX is in a favorable mesoscale environment for tornadoes and will likely continue for the next hour.


DISCUSSION...As of 2015 UTC, hi-res radar imagery showed a well-developed supercell over portions of Coryell county Texas. Based on an STP environment around 3 and VROT greater than 70kt, there is the potential for this storm to produce a strong tornado. VAD winds AT GRK at 925 MB have increased and backed to 35 kt from the south, supporting greater low-level shear with strong buoyancy (3000 J/kg of MLCAPE). Additional storm development along the southwestern flank of the storm may eventually favor upscale growth into a bowing MCS. However, this intense supercells is likely to persist in an environment favorable for a strong tornado for at least the next hour as it moves southeast.


   ..Lyons.. 04/28/2023

Mesoscale Discussion #767


Mesoscale Discussion 0767

   NWS Storm Prediction Center Norman OK

   0542 PM CDT Thu May 11 2023


   Areas affected...Parts of south-central Oklahoma


   Concerning...Tornado Watch 213...


   Valid 112242Z - 120015Z


   The severe weather threat for Tornado Watch 213 continues.


   SUMMARY...The greatest near-term supercell tornado threat should be

   focused over portions of south-central Oklahoma between I-44 and I-35 during the next couple of hours.


DISCUSSION...Latest radar data from KFDR shows an evolving discrete supercell in Cotton County, OK -- where surface convergence is maximized along the intersection of a remnant outflow boundary and differential heating boundary. Additional discrete updrafts are also developing northward along the boundary into Comanche County. Ahead of this activity, visible satellite imagery shows billow clouds transitioning to HCRs, indicative of recovering outflow-modified air. Continued recovery/destabilization amid lower 70s dewpoints should favor continued intensification of the ongoing updrafts during the next couple of hours -- and weak large-scale ascent should favor a continued discrete mode. During the next couple of hours, a strengthening nocturnal low-level jet should favor larger, clockwise-turning low-level hodographs (150-200 m2/s2 effective SRH) -- supportive of longer-lived mesocyclones and a corresponding increase in supercell tornado threat.


..Weinman.. 05/11/2023

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